1990 deville missing

It runs perfect until it gets hot then it starts to miss and it wont idle right.it loses alot of power,it feels like as if you would pull 1 of the plug wires off and try to run it
I have replaced the plugs,wires,distributer cap,rotor button,ignition controll module, coil, fuel pump, fuel filter
and also i just bought the car and it has only had about 300 miles put on it since 2009

if anyone can help thanks

i checked for codes but there is none

i also just noticed that the exhaust is getting super hot, it seems like its the whole exhaust, i ran it about 3 miles and it was like this

If it is a dead miss, you could kill one cylinder at a time until the one that does not change the rpms is the suspect cyl., then look at that plug/wire. If it has good spark, do a compression test. Also watch for any vacuum leaks although temps would not affect that.